I haven't yet been able to replace my single glazed windows and I have a tendancy to feel closed in with no natural light so total coverage with winddow quilts just didn't work for me. When I found this site I was ecstatic. Bubble glazing. I'm not sure I'll be able to go the full route with metal tracks or wooden frames this year but will definately use the bubble glaze idea. Just thought I'd share with others that might be interested in the idea, too.